Overview
Mumps is an acute infectious disease characterised by bilateral parotid swelling caused by an RNA paramyxovirus.
Transmission
- It is spread by respiratory droplets, fomites, or saliva
- The incubation period is around 12-25 days
- The most infectious period is around 1-2 days before symptoms to around day 9 onwards
Nearly all people develop lifelong immunity to mumps after one episode, but reinfection is possible.
Pathogenesis
The virus infects the respiratory tract cells and replicates in the respiratory tract. It then spreads to the parotid glands causing parotitis. It is thought to then spread to the lymph nodes and then to the blood, where it travels to distal sites including the testes, which can cause orchitis.
Epidemiology
- Children <1 year old rarely get mumps as they usually have passive immunity from the placental transfer of maternal antibodies
- Following the introduction of the measles, mumps, and rubella (MMR) vaccine, the incidence of mumps has dropped significantly
- The efficacy of the MMR vaccine is around 80%
Presentation
Mumps presents with:
- Parotitis – present in 95% of symptomatic cases
- Usually, one gland is affected first and peaks in size after 2-3 days before the other parotid gland follows. Around 75% of people have bilateral parotitis
- This can also lead to earache, difficulty with pronunciation, and chewing
- There may be a prodrome of non-specific features – usually 1 day before parotitis and peak around the time parotitis is at its worst:
- Fever, malaise, headaches, anorexia, muscle ache
- Complications, which may appear without parotitis – discussed below
Investigations
The diagnosis is clinical and confirmed by testing saliva for IgM mumps antibodies.
Management
Overview
Treatment is supportive and involves rest and using paracetamol for fever and pain.
Notify Public Health England in all cases of mumps, even before laboratory testing as mumps is a notifiable disease.
Children should be excluded from school for 5 days after parotid gland swelling occurs.
Patient Advice
Patients are usually followed up around 1 week after parotitis occurs to check that symptoms are resolving or have resolved.
Patients should seek help if features of the following develop:
- Meningitis – headache, vomiting, neck stiffness, altered consciousness, seizures, photophobia
- Epididymo-orchitis – painful and swollen testicles
Complications
- Epididymo-orchitis – the most common cause in up to 38% of men
- Can contribute to subfertility and infertility
- Up to 50% of people have some degree of testicular atrophy
- Usually occurs around 4-5 days after the onset of parotitis
- Encephalitis – around 0.1% of cases
- Oophoritis – around 7% of women
- Rarely causes infertility or premature menopause
- Aseptic meningitis – around 25% of cases
- Almost all patients recover with no residual neurological defects
- Myocardial complications – ECG changes occur in around 15% of cases
- Transient hearing loss – around 4% of cases
- Pancreatitis – around 4% of cases
Prognosis
- Mumps is usually self-limiting and resolves in around 1-2 weeks
- Complications are more common in adults than children
